Biomolecular conjugates can be used in immunoassays for detecting specific target molecules in a sample. Various conjugates are known, including antibody-detectable label conjugates and antibody-enzyme conjugates, and a number of methods have been developed for making these conjugates. For example, antibody conjugates often are prepared using coupling reagents having at least two reactive groups. One of the groups is used to couple to the antibody, and another functional group is coupled to the detectable label. These coupling reactions can interfere with the performance of the conjugate for a desired purpose. For example, coupling can deactivate antibody-enzyme conjugates, such as through steric effects, deactivation of reactive functional groups critical for appropriate functioning, changes in solubility, etc. As a result, and despite prior efforts, there still is a need for molecular conjugates, and methods for their production and use, that provide greater assay sensitivity. Ventana Medical is the assignee of a number of patents and applications in this general area, including: U.S. patent application Ser. No. 11/018,897, entitled Microwave Mediated Synthesis of Nucleic Acid Probes, published as U.S. publication No. 2005/0158770, on Jul. 21, 2005; U.S. Provisional Application No. 60/739,794, filed on Nov. 23, 2005, and the corresponding utility application Ser. No. 11/603,425, entitled “Molecular Conjugate;” U.S. Provisional Application No. 60/856,133, and the corresponding utility application Ser. No. 11/982,627, entitled “Haptens, Hapten Conjugates, Compositions Thereof and Method for their Preparation and Use.” Each of these prior applications is incorporated herein by reference. Example 12 of the '897 patent discloses one method for making polyacrylamide hydrazide. The '897 patent application states that the “invention provides a method for preparing a labeled cytosine, a labeled cytidine, or labeled cytidine-containing biomolecule, such as oligonucleotides, DNA molecules, RNA molecules, proteins, peptides, or other biomolecules.” U.S. Patent Publication No. 2005/0158770, paragraph 0044. Moreover, the application states that “[l]inear polymers that are functionalized with fluorophores and nuclelophillic group(s) may also function as useful reporter containing moities.” And “a preferred functionalized polymer is polyacrylamide hydrazide functionalized with fluorophores, particularly PAH of MW 10,000 to 20,000 bearing between 10 to 40 hydrazide groups per polymer chain.” U.S. Patent Publication No. 2005/0158770, paragraph 0068. Reporter groups are defined to include “any detectable moiety commonly used for labeling probes,” including haptens and proteins. U.S. Patent Publication No. 2005/0158770, paragraph 0053.
According to Scheme 11 of the '425 application, the Fc portion of an antibody is oxidized to form an aldehyde, and a thiolated hydrazide is then coupled to the Fc portion of the antibody by reaction of a hydrazide nitrogen with the carbonyl. According to Scheme 13 of the '425 application, a thiolated hydrazide coupled to the oxidized Fc portion of an antibody is reacted with alkaline phosphatase having a thiol-reactive functional group to form a conjugate. And, according to Scheme 19, a polyacrylamide hydrazide is first synthesized, and then, as stated in Example 22:                In an appropriate solvent, the resulting PAH is reacted with a thiolating agent, such as thiol-dPEG-NHS ester1 (Quanta Biodesign, Powell, Ohio) or Traut's reagent, to thiolate a portion (for example, approximately 50-75%) of available hydrazides (z=5 to 40) and provide a polymeric multifunctional hydrazide thiol linker that can be used in the disclosed method. 1Applicants note that the reagent should be referred to as S-acetyl-dPEG-NHS ester.As presently understood, all embodiments of the PAH conjugates disclosed in the '897 application have at least a portion of the reactive hydrazide functional groups thiolated as disclosed in Example 22. Moreover, it is the thiol group, provided by thiolation of the hydrazide, that is the reactive moiety used to form conjugates.        